The invention relates to marking jet discharging head, particularly for apparatus for the marking of objects. In another aspect it relates to such marking apparatus.
One type of marking apparatus for applying symbols and inscriptions to packages or other articles uses a discharging head having jet orifices which are arranged in a row and which are briefly actuated in an electronically controlled sequence and discharge dots of marking colour material which together form the desired symbol or inscription on to the package as the latter is being conducted past. The row of jet orifices either are supplied with colour through colour conduits which are opened and closed by electromagnetic valves, or they communicate directly with a colour chamber and their orifice opening facing towards the colour chamber is closed by a closure element which is arranged on the rod of a push element which briefly lifts the closure element away from the orifice opening and presses it back again on to the said opening to squirt a small quantity of colour from the orifice. Since the colour jet orifices have to be arranged in a row near one another if the dots of colour which they discharge are to produce a legible configuration, only very little room is available behind the colour jet orifices for the push elements, so that these can be given only very small dimensions. If electromagnets are used as the push elements, because of the small dimensions which are all that can be allowed the electromagnets are of relatively low power and have a small pushing force, so that they produce a small application pressure on the closure elements. Therefore, faults readily occur in the sequence of operations. The colour jet orifices also have to be at a certain minimum spacing from one another which is determined by the push devices, so that the minimum practicable height of the inscription is limited.
Preferred embodiments of the invention obviate or ameliorate these disadvantages and may provide discharging heads in which orifices can be arranged very near to one another, and reliable opening and closing of each individual jet orifice is guaranteed.